Several ecology students were tracking the population ranges of two species of squirrels that live in the Cascade Range of Oregon. These students noted that when both species of squirrels were present in a region, species A could be found from sea level to about 900 feet above sea level, and species B could be found from about 900 feet to 1,500 feet above sea level. However, when species B was found alone, it had a range of about 500 feet to 1,500 feet above sea level. This is an example of
A) predator avoidance.
B) competitive exclusion.
C) habitat fragmentation.
D) parasitism.
E) coevolution.

Question

Quizplus · Accepted Answer

This scenario is an example of competitive exclusion, where two species compete for the same resources but cannot coexist at constant population values; one species will often displace the other. In this case, when both species are present, their ranges do not overlap, suggesting competition for resources at the boundary of their respective ranges. When species B is alone, its range expands, indicating it was excluded from the lower altitudes by species A when they coexisted.

Several Ecology Students Were Tracking the Population Ranges of Two